Arc quencher



June 3, 1941 H. c. GRAVES, JR 1 ARC QUENCHER Filed July 31. 1940 2Sheets-Sheet l INVENTOR Mal C. 51mm .lY 2 E &

ATTORNEY June 3, 1941.

H. c. GRAVES, JR 2,244,061

ARC QUENCHER Filed July 31, 1940 2 Sheets-Sheet 2 60 1, 554,-: 72 72a.42a 53. L: 5/. 4- 73a 43;; -40b.

INVENTOR n Macaw it.

ATTORNEY Patented June 3, 1941 sac oomzcnaa Herbert G. Graves, 1r., WestChester, Pa., assignor to I. T. E. Circuit Breaker ()ompany,Philadelphia, Pa., a corporation Pennsylvania Application July 31, 1940,Serial No. 348,717

19 Claims.

This invention relates to switch gear and circuit interrupters and moreparticularly to are extinguishers therefor, the said are extinguishersbeing of the spaced plate type wherein a plurality of spaced metalplates of preferably magnetic material are utilized to quench the arc.

The spaced metal plates are arranged in substantially parallelrelationship to each other, each of them being substantially at rightangles to the path of the arc and having a series of registered notchestherein through which the arc is initially drawn.

The flow of current in the arc produces a magnetic field surrounding thecurrent path. Where plates of magnetic material embrace the are theyform a path of low reluctance for this flux. The reaction of the flux onthe current pulls the are into the notch and onto the metal plates. Thisbreaks up the are into a plurality of short arcs in series, which themagnetic field continues to move along the plates at sufilcient speed soas to prevent the plates at the arc terminal from reaching excessivetemperature. The breaking up of the are into a series of short arcsfacilitates extinguishment and reduces the possibility of an alternatingcurrent are restriking after the current has passed through zero.

This action of the plates in moving the arc is augmented by the factthat the path of the current through the circuit breaker and the arc isin the form of a partial loop. A current flowing in such a path tends toenlarge its loop due to the concentration of fiux lines within the loop.

Heretofore, insulating sidewalls for supporting the plates have beenmolded into the necessary shape for supporting'the arc quenching plateseither by molding notches therein or by inserting the plates during themolding operation or by other similar means.

The use of molded insulating sidewalls, however, necessitates arelatively thick material because of limitations in the moldingoperation itself and moreover there is a lack of flexibility in shapingthese supporting walls to any suitable form.

I have discovered that by replacing molded insulating walls by thinbendable sheet material, I secure greater flexibility which enables meto bend the walls to any desired shape which may be suitable forsupporting the arc quenching plates. Moreover, I may employ much thinnermaterial for these side walls thus reserving a greater amount of spacefor the actual anc quenching plates.

This construction by increasing the plate area, increases the thermalcapacity of the unit so that the temperature of the plates is raisedless for each circuit interruption than is the case in prior arcquenching units.

An important object of the present invention,

therefore, is to provide in arc quenchers of the spaced plate typesupporting side walls for the spaced plates of thin bendable sheetmaterial.

Another important object of the present invention'is, in connection withthe use of. such side walls of bendable sheet material, to provide aconstruction which increases the effective are interrupting plate areaof the arc quencher without necessarily increasing the over-alldimensions or size of the unit.

A corollary object, therefore, is to provide a construction whichinherently permits a greater interrupting plate area for a specificvolume and hence increases the effectiveness of the arc quenching unitor makes possible a reduction in size, should that be desired.

The advantage flowing from this result is that when the arc quenchingunit of the design of the present invention is used on a 600 voltcircuit carrying a normal load of 600 amperes in a type of interrupterwhich normally in modern commercial design is expected to have a ratedinterrupting capacity of 20,000 amperes, the unit of the presentinvention, contained within the dimensions of the prior types ofquenchers may be conservatively rated at 40,000 amperes and, in fact,has been able to interrupt 50,000 amperes or more without failure.

Heretofore, it has been necessary to utilize additional insulatingpieces to protect the legs of the arc quenching plates or to make themold sufilciently thick so that the legs of the arc quenching plates maybe embedded therein and thus protected from the direct effect of theare.

In the present invention I have found that the thin bendable insulatingsheet material may be bent around the legs defining the notch of the arcquenching plates and thus afford a simple easily manufactured protectiontherefore.

An object of this invention'therefore is to provide a simplified meansfor protecting the legs defining the notches of the arc quenching platesfrom damage by the are when it is first drawn.

Since the walls which position the plates are of thin bendable sheetmaterial, I have found it advantageous to brace and support the wallsthemselves; and for this purpose instead of using additional structure,I have found that the plates which are positioned by the thin insulatingwalls and the insulating walls themselves may interbrace each other toform a unitary whole.

Still a further object of this invention, therefore, is the provision inan. arc quenching unit of spaced arc quenching plates and insulatingwalls therefor which interbrace and support each other.

At the top of the stack of plates which frequently are arrangedvertically, as shown in the drawings, that is, with their planes in avertical position, there has been provided in the present invention acover with vents through which the portion of Figure 1 and are gases'mayescape. In the preferred modification, these vents are aligned with theapices of the notches in the plates, which notches are substantiallycentrally disposed within the plates themselves. v v

The location of the vents tends to cause the maximum gas velocity tooccur in the central plane of the unit and hence along the notches. Thisaction drives the are rapidly into the narrow part of the notches whereheat is absorbed and then on to the plates when further cooling occurs.

These vents are not formed as a continuous slot but rather as a seriesof spaced holes preferably arranged so that they may be aligned with theplane of the apices of the notches.v

It is entirely probable, although it is difficult to ascertain, thatthese holes forming a discontinuous slot, contribute toward thequenching of the arc lay-permitting shunt paths of ionized gas to formover the top. Such shunt paths may cause instability of the are as thecurrent approaches zero.

It is, therefore, a further object of the present invention to provide aseries of spaced vents aligned with the apices of the notches in thespaced magnetizable plates.

Still another object of the invention is the provision of a simplifiedand novel type of arcing horn which may be integrally associated withthe are quenching unit and connected into the arcing circuit in asimplified manner.

These and many other objects of this invention will in part be apparentand in part pointed out in the following description and drawings, inwhich:

Figure l is a view partly in cross-section showing a circuitinterrupting apparatus with the arc quenching unit of the presentinvention in place.

Figure 2 is an exploded view in perspective showing the arc quenchingunit and the means of mounting the same on the panel together with themeansfor connecting the arcing horn thereof into the circuit.

Figure 3 is a cross-sectional view of the arc quenching unit showing anenlargement of a taken on line 33 of Figure 4.

Figure 4 is an elevational view of the front of the are quenching unittaken along line 4-4 of Figure 3. v

Figure5isaplanviewofthebaseplate of the arc quenching unit for attachingthe unit to the panel.

Figure 6 is aplan' view of a magnetizable plate.

Figures 7 and 8 are plan views of modified forms of top plates.

Referring now to Figure 1, thereis here shown a circuit interrupterhaving circuit connecting members Ill and I I which are secured in anysuitable manner to portions of the circuit interrupter casing l2.

Current is led from the circuit connecting member to the connectionstrap I3 and thence to the stationary main contact H from which itpasses to the movable main contact l5 and through the lead I to theterminal II which is appropriately connected to theconnecting member Thecontact I5 is mounted on a movable arm ated by the. handle 20 or by anysuitable automatic tripping or closing apparatus.

A movable arcing contact 2| is also carried by the movable arm I! and isengageable with an appropriate stationary arcing contact 22 mounted onthe plate I30 which is connected to the connection strap I3.

The particular form of circuit interrupter contained within the casingl2 and the specific operation thereof forms no part of the presentinvention, but these members have been indicated in order to show acomplete operative structure in which the arc quenching unit 30 of thepresent invention may be used. I

The are quenching unit 30 (see Figures 2, 3 and 4) comprises a pair of.insulating side walls 3| and 3|a of bendable sheet material, having aseries of preferably rectangular perforations 32 to cooperate with lugson the metal plates mounted between the walls.

The metal plates 40, each having the form shown in Figure 6, arepreferably of magnetizable material. Each plate has a notch 4| and apair of legs 42 and 43 on each side of and beneath the notch. The wallsof the notch 4| converge toward each other and terminate in the.

slot portion 44, the walls of which are substantially parallel.

Each plate is reversed with respect to its adjacent plate.

Each plate has a shoulder 45 projecting from the edge 46 midway betweenthe top and the bottom thereof with a lug 41 projecting from theshoulder. Each plate also has extending from the opposite edge 49, theshoulder 54 near the top and the shoulder 5| near the bottom which carryrespectively lugs 52 and 53. The top edge 55 of each plate also has ashoulder 58 near one end of the edge which carries a lug or extension51. A comer of the plate adjacent the shoulder 58 and lug 51 is cut outat 58 to provide an additional passage for the flow of arc gases. Sinceadjacent plates are reversed, the passage is not continuous and thus anarc will not-restrike therethrough.

Plate 40a (Figures 3 and 4) is so positioned that shoulders 50a and5|a-of edge 49a abut against the inner side of wall 3| and so thatshoulder 45a of edge 46:: abuts against the inner side of wall ila: andthe respective lugs 52a, 53a and 450 project through the perforations 32in the walls. The cut-out 58a is arranged at th upper right corner.

Plate 40b is mounted in reversed position with respect to plate a sothat the shoulders 50b and. Ilb abut against the inner surface of wallIla and so that the lugs 52!: and 53!; project through perforations inthe wall 3|a, while ll which is mounted on an insulated shaft I!contacts.- The insulated shaft ll may be oper-' each plate are displacedwith respect to corre-' sponding-notches and slots in adjacent platesowing to the fact that the notches 4| and their associated andcommunicating slots 44 are slightly asymmetrically arranged oroff-center with respect to a line drawn exactly between and parallel toedges 48 and 45. 7

Thus notch 4|a. of plate 40a and slot 440 of plate a are displaced withrespect to notch lib and slot b of plate b (see Figure 4). The

- notch ll and slot ll of plate llc are arranged to exactly underly thecorresponding notch and slot of plate a; While the notch H and slot H ofplate 40d are arranged to register with those of plate 40b.

This prduces a narrow aligned notch 60 formed by the registering notches4|, the said aligned notch being narrower than each of the notches 4|;and also produces an aligned slot "formed by the registering slots H,the aligned slot 5| being narrower than each of the slots 44.

By this means a more rugged die may be used to punch out the notches andtheir communicating slots while still making it possible to obtain arelatively narrow aligned notch and slot arrangement which will morereadily restrict the increase the magnetic path for the formation ofmagnetic flux. Leg 2 is not necessary for the positioning of the sidewall since a plurality of legs 43, by reason of the reversing of theplates, are aligned on each side of the arc path or notch and thusprovide full support for the ends 12 and 12a walls 3| and Bla.

When the side walls and the plates are interlocked with the lugs 41, 52,and 53 of the plates extending through perforation 32 of the walls andthe ends of the walls hold in the slots III of the plates, then theparts may be permanently secu-red together by twisting, spreading,riveting over or otherwise deforming each lug so that an appropriatebearing surface will be formed thereby against the outer surface of thewalls to prevent the lugs from slipping out of the perforations.

The back plate 80 having the form shown in Figure 5 is secured in theposition shown in Figures 2, 3 and 4, bylugs BI and 82 of edge 83 andlug 84 of edge 85 which lugs extend through the perforations 32 in theside walls, and are appropriately deformed.

Plate 80 has a cutout 86 to register with the arcing horn 22 and a notch81 communicating with the cutout 86 for engaging the locking member 88,Figure 2, in the manner hereinafter described.

The back plate also has a .portion 89 extended beyond the top of the arcquenching unit, this extension having a notch 90 which may be engaged bythe head of a suitable screw 9| (Figure 2) for completing the securementof the unit to the panel in the manner hereinafter described.

It should now be noted that the legs 42 and 43 of the plates 40 providenot merely a means for positioning ends II of the side walls, but alsofurnish additional areas of magnetic material which increase thecross-sectional area of the path for the magnetic flux and thusaccelerate the upward movement of the arc. The aligned notches ll withtheir communicating slots 44 provide a means for first compressing thearc and cooling it. The arc is then broken into a series of short arcsas it travels onto the metal plates.

As previously described, the flow of current in the arc produces amagnetic field surroundin the current path. The plates of magnetizablematerial form a low reluctance path for the flux. The are is pulled intotheplates where it-is broken rinto a series of short arcs and movedalong the .plates at suflicient speed to prevent the plates fromreaching an excessive temperature. Extinguishment is thus facilitated,and possibility of a restriking of the arc is reduced.

, Since a bendable insulating sheet which embraces portions of theplates is used, a greater area is posible for each of the plates withinstandard over-all dimensions for the arc quencher as a whole, thusincreasing the strength of the magnetic field and causing greater andmore rapid movement of the arc.

In previous arc chutes designed for interrupting high values of current,it was found advisable to protect the ends of the legs of the magneticplates from the arc. This was done by making the side walls of aninsulating material which when in a plastic condition, could be pressedin a mold to the required shape and then caused to harden as by thesetting-of a cement or binder. Due to the nature of the process and thephysical characteristics of the resulting material, these parts requireda minimum thickness of a quarter of an inch or more. The constructionshown in the present application provides superior protection for thelegs of the plate and permits the use of a thin bendable inexpensivematerial. The material now used is less than a sixteenth of an inchthick. Thus, instead of requiring one half inch of width for both theside plates, less than one eighth of an inch is used with acorresponding increase in plate width. The width of the plates in an arcquencher having an outside width of 2 is, therefore, increased from 1 to2" or 25.6% for the same overall width of the assembly. In addition tothis, the use of thin sheet material as hereinafter described over thetop of the arc chute permits longer. metal plates to be used. Theincrease in area of the-plates that may be thus obtained, is 45.2%. Theadded height increases the distance from the top of the slot to the topedge of the plate by one quarter of an inch, thus giving a greatercooling surface.

As is seen more particularly in Figure 2, a top plate I00 is secured tothe arc chute by the lugs 51 which pass through appropriate perforationstherein. These lugs 51 are also twisted or deformed in the same manneras are lugs 41, 52 and 53 in order to secure the top plate I00 inposition. Each side of the plate I" is supported by lugs 51, the lugs 51in adjacent plates being staggered with respect to each other owing tothe reversal of adjacent plates.

Vents are provided in the top plate I. These vents consist primarily ofcircular openings or perforations of substantial size along the centerline of the plate. These vents III are so arranged that they are abovethe apices of the notches 4| and their slots 44 and thus provide for avent along the line or area of greatest speed of the discharged gases.

The location of the vents tends to cause the maximum gas velocity tooccur in the central plane of the unit and hence along the slots. Thisaction drives the are rapidly into the narrow part of the notches. wherethe heat is absorbed, and so on to the plates.

Instead of using a continuous slot oreven an open space along the. topwall the vents Ill have closed areas III between them. This has beenfound to be more eflicient apparently for the reason that a series ofshort shunt arcs are probably produced from vent to vent around thespaces III, thus making the are even more unstable. The reason for theberzeficial result obtained is not quite clear. And yet, using atopplate I h'aving vents IIO separated by short intervals III in connectionwith an arc chute of the type herein described, it has been possible toobtain an interrupting capacity on a 600 volt circuii; normally carryinga maximum of 600 amperes oi as high as 50,000 amperes without failure byusing an arc chute, the over-all dimensions of which are no greater thanthose of arc chutes previously usable at interrupting capacities of only20,000 amperes or thereabouts;

It should be noted that the top plate I00 is cut out at I13 so thatthese cutouts may register with slight extensions III of the insulatingside walls 3| and 3Ia to help position the top plate I00 andcorrespondingly the longitudinal extensions In of the top plate I00register between the extensions III--III on the side walls in orderfurther accurately to position the top plate I00 and to interbrace thestructure and prevent skewing thereof.

While the circular vents III) are preferred, other types of vents suchas those seen in the views of Figures 7 and 8 may be utilized. Thus, inFigure 7, the vents 2I0 in the top plate 200 the lead I21 (Figures 2and 1) to the arcing horn. The lead I21 connects the arcing horn I20with the terminal I'I.

Stationary arcing contact 22 is mounted on plate I30 which is secured inany suitable manner to the connection strap I3. Plate I30 is separatedby an insulating strip I3I from the con nection strap I3 but theextension I32 of the plate I30 forms a base for the stationary contactI4. This extension I32 is also in contact with the connection strap l3thus providing. a suitable may be slots transversely arranged andslightly diagonal; or as in Figure 8, a double row of slots may be used.This increases the area of the top plate through which gases may playand may permit shunt arcs to play over a greater portion of the topsurface.

In each case the vents are so arranged that they flt in with thepatternof the staggered stakes or lugs 51 and thus do not interfere withsecurement of the top plate to the arc quenching structure.

The top plate has also a structural p p se, since its interlocking withthe side walls and its securement to the plates prevents any skewing orthe plates with respect to the side walls.

An arcing horn I20, Figures 1 and 3, is provided in conjunction. withthe arc chute, the said arcing horn being mounted on the front plateI2I. The front plate I 2I is not secured to the side walls 3I and 3Iabut instead is mounted on the plate 40a by means of rivets I22, I22having insulating bushings I23 and washers which effectively insulatethe plate I2I from the plate 40a.

The arcing horn is connected to the lower terminal oi the circuitbreaker so that during arcing, the arc maybe transferred to this horn,shunting out the moving contact. The are horn plate is spaced fromthesides and the top of the housing. This is done so that when thecircuit breaker is opened, there will be full voltage between the upperterminal and the lower terminal, Since the outer arcing horn isconnected to the lower terminal, there will be full voltage between theouter arcing horn and "the back, or supporting plate of the arc chute.By providing the construction shown, the possibility oi leakage alongthe fibre housing is greatly reduced.

The arcing horn I20, as seen in Figures 1 and 3, projects into thearcing path formed by the registering notches ll of the aligned parallelplates 40. The arcing -horn I20 and the plate I2I aredrilled andthreaded at I25 in order to receive the screw I26 (Figure 2) whichattaches path for the current from the connecting member I0 through thestrap I3 to the stationary main contacts I4 and the stationary arcingcontact 22.

The stationary arcing contact 22 is adjacent the securing member whichalso serves in part as a stationary arcing horn since it is aligned withthe arcing path produced by the aligned slots in the magnetic plates.

The arc quencher as a unit may be secured to the plate I30 by means 01the notch 81 in the base plate 80, see Figure 5, which is engageablearound the post I40 which cooperates to support the member 80, while theportion HI 0! the member 80 projects beyond the notch 81 in order toengage the opposite or inner surface of the base plate 00.

The screws Si is passed through the notch of the base plate 30 into thethreaded opening I00 in the plate I30, thus completing the attachment ofthe arc quenching unit.

Subsequently, the arcing horn I20 is connected into the circuit byplacing the end I5I of the lead I21 (Figure 2) over the opening I25(Figure 3) in the arcing horn I20 and passing the screw I26 through theperforation I53 in the end I5I of the lead and into the threaded openingI20.

The are quenching unit after the completion 'of'this operationis readyfor use in the circuit interrupter.

The edges I00IOI of the insulating side walls 3 I and 3Ia (see Figures 2and 3) extend beyond the base plate 80 and abut the insulating sheet IIIon either side of the plate I30, thus further serving toposition the arcquenching unit in place and also providing for further interphaseinsulation.

In operation of the arc quencher, the aligned notches form the path ofthe arc.

When the movable contactcarrylng arm I8 is caused to move toward theopen circuit position wherein the contacts are separated, normally themovable contacts I4 and I0 are separated first so that the arc is drawnbetween the movable arcing contact 2| and the stationary arcing contact22.

During the opening movement of the arcing contacts an arc is initiatedat the final point of separation, which is at the uppermost points ofthe stationary and moving elements. Thus the initial point of gas'generation, which is substantially explosive in action, occurs at apoint above the edges I0 of the return bend of the side walls. Theintense heat generation in the initial arc produces a high gas pressureand hence radial velocity of gas. The downward flow of gas is preventedin the center, by the contacts themselves, particularly at, and shortlyafter the initial separation and, at the sides, by the return bends oithe side walls. An influence is, therefore, produced to increase thelateral and vertical velocities of the gas. This action tends to drivethe are more rapidly up through the notches and onto the plates, hencecontributing to quick extinguishment' of the arc.

The end of the arc is transferredfrom the movable arcing contact 2| tothe stationary arc-' ing horn I20 mounted on the plate III.

The end of the are which plays upon the, stationary arcing contact 22 isalso transferred by the magnetic held onto the member II which becomes astationary arcing horn.

When the arc enters the plates, it is broken into a series of short arcsand quenched. In the event that it moves beyond the upper edges of theplates, then the arc gases may vent through the openings III in the topplate (or the openings II. in top plate I, or openings 3|. in top plate3") and short shunt arcs may be established from opening to opening,thus rendering the are even more unstable so that it may readily bequenched.

The plate ill is cut out at I50 where a portion of it would beregistered with and aligned with the opposite arcing born 88, thusmaking it even more dimcult for the arc to play between these members.This opening also served as a vent to relieve the gas pressure incidentto current interruption and thus reduces the possibility of hot gasesbeing blown down toward the breaker mechanism.

Since the insulating side walls are of bendable sheet material whichembraces portions of the plates and these permit increased plate area,the arc quenching action is enhanced.

The legs 43 and 42 of the plates which extend into the bent-aroundportions of the side walls enhance the magnetic effect by an additionalarea while the other portions of the plates by reason of their greaterarea can have the effect above noted.

The are quenching unit is simple in construction and readily attachableto the unit. Thus during the manufacture bent ends I2 of the walls maybe inserted in the aligned slots III and the perforations in the sidewalls may engage the lugs of the plates. The lugs are twisted orotherwise deformed to make the engagement permanent. The top'wall isthen mounted in place and the lugs also twisted or otherwise deformed.The bottom wall may be mounted in place at the same time as the platesare mounted. The plate "a may have the front member Ill secured theretobefore the said plate 400 is secured in the stack.

There has here been described a physical form v and actual embodiment ofan arc quencher whichby comparison with other units of the same over-alldimensions has more than twice the interrupting capacity of such otherunits. The actual reason for this vastly increased interrupting capacitymay lie in any one of the elements hereinabove described or may actuallyinhere in only the combination thereof or in only a combination ofcertain portions of said elements. The action of the are when it isbeing quenched is so rapid as to make it, at the very least, difficultto determine the above described are quencher, should move more than%."4" apart to interrupt high currents in a very short arcing time.

In each of the foregoing portions of the de-' scrlption there has beendescribed the, preferred embodiment which actually hasbeen found to besuccessful at for instance currents of 600 volts carrying a normal loadof 600 amperes where its interrupting capacity was as high as 50,000ameach of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said are quencher, said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; said side walls being of bendable insulating sheetmaterial, the ends of said side walls extending beyond said legs beingbent around the ends of said legs and into the entrances to saidnotches,

and means on said plates for securing said bent portions of said sidewalls in bent position.

2. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs'defining each.notch;corresponding legs on corresponding sides of the plates being alignedwith each other;

opposed side walls for said are quencher; said plates being each normalto and supported by said side walls at the outer edges of said plates;extensions from; the outer edges of said plates extending through saidside walls and securing said plates and side walls together, said sidewalls being of bendable insulating sheet material, the ends of said sidewalls extending beyond said legs being bent around the ends of said legsand into the entrances to said notches, and means on said plates forsecuring said bent portions of said side walls in bent position.

3. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each otherpopposed side walls for said are quencher; said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; extensions from the outer edges of said plates extendingthrough said side walls and securing said plates and side wallstogether, and said extensions having shoulders at their bases forspacing the outer edges of the plates from the side walls, said sidewalls being of bendable insulating sheet material, the ends of said sidewalls extending beyond said legs being bent around the ends of said legsand into the entrances to said notches, and means on said plates forsecuring said bent portions of said side walls in bent podtion. I l

4. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned-to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said arc quencher; said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; extensions from the outer edges of said plates extendingthrough said side walls and securing said plates and side wallstogether, said extensions from opposite edges of the plates beingstaggered with respect to each other; said plates being arranged so thatadjacent plates are reversed with respect to each other wherebyextensions through each side wall are staggered, a top plate secured tothe ends of said notched plates and engaging said side walls; said topplate, notched plates and side walls interbracing and supporting eachother.

5. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said are quencher; said platesbeing each normal to and supportedby said side walls at the outeredgesof said plates; said side-walls being of bendable insulating sheetmaterial, the ends of said side walls extending beyond said legs beingbent around the ends of said legs and into the entrances to saidnotches, certain of the legs on each side of the arcing path defined bythe aligned notches having a slot on the inner notch-defining boundarythereof engaging the free end of the bent around portion of the sidewall.

6. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said are quencher; said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; said side walls being of bendable insulating sheetmaterial, the ends of said side walls extending beyond said legs beingbent around the ends of said legs and into the entrances to saidnotches, one leg of each plate having a slot on the inner notch-definingboundary thereof engaging the free end of the bent around portion of theside wall, adjacent plates being reversed with respect to each otherwhereby the free end of each side wall is engaged by certain of saidslots.

'7. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said are quencher; said platesbeing each normal to and supported by said side walls at the outer edgesof said plates;

. said side walls being of bendable insulating sheet material, the endsof said side walls extending beyond said legs being bent around the endsof said legs and into the entrances to said notches, and means on saidplates for securing said bent portions of said side walls in bentposition, each notch in each plate being asymmetric with respect to thecenter line of the plate which runs through the notch, adjoining platesbeing reversed with respect to each other, a restricted portion of eachnotch being aligned with restricted portions of each of the othernotches.

8. In an arc quenching structure, having a plurality of spaced plates,9. housing therefor comprising a side wall of bendable sheet insulatingmaterial, means for securing said spaced plates to said side wall, anend of said side wall being re-entrantly bent into a U-shapedreinforcing channel, and means for securing said end of said Side wallin said U-shaped reinforcing position.

9. In an arc quenching structure, having a plurality of spaced plates,9. housing therefor comprising a side wall of bendable sheet insulatingmaterial, means for securing said spaced plates to said side wall, anend of said side wall being re-entrantly bent into a U-shapedreinforcing channel, and means on said spaced plates engaging said endof said side wall and secur ing said end in said U-shaped reinforcingposition.

10. In an arc quenching structure, a plurality of spaced substantiallyrectangular plates, each plate having a notch extending from one edgethereof defined by legs, said notches being substantially aligned anddefining an arcing path; housing means for positioning said plates inspaced relationship, said housing means enclosing the unnotched edges ofsaid plates and embracing the ends of said legs; and an opening in awall of said housing, said opening being substantially aligned with andintersecting the plane of the axis of said notches through the apicesthereof.

11. In an arc quenching structure, a plurality of spaced substantiallyrectangular plates, each plate having a notch extending from one edgethereof, said notches being substantially aligned and defining an arcingpath; housing means for supporting said plates in spaced relationshipand enclosing the unnotched edges of said plates;

'said housing comprising a. pair of opposed side walls and a top wall,each of insulating material and ach secured to said plates, the said topwall being interlocked with said side walls, and an opening in a wall ofsaid housing, said opening being substantially aligned with andintersecting the plane of the axis of said notches through the apicesthereof.

12. In an arc quenching structure, a plurality of spaced substantiallyrectangular plates, each plate having a notch extending from one edgethereof defined by legs, said notches being substantially aligned anddefining an arcing path; housing means for positioning said plates inspaced relationship, said housing means enclosing the unnotched edges ofsaid plates and em: bracing the ends of said legs and a plurality ofopenings in a wall of said housing for egress of arc gases, saidopenings being substantially aligned with and intersecting th plane ofthe axis of said notches through the apices thereof,

said notch and defining a projection of said plate,

said projection extending in the plane-of said plate toward the edge ofsaid plate with winch said notch communicates; the center line of saidhousing means for positioning said plates in spaced relationship, saidhousing means enclosing the imnotched edges of said plates; integralextensions-of said housing embracing the ends of said legs; and anopening in a wall of said housmg, said opening being substantiallyaligned with and intersecting the plane of the axis of said notchesthrough the apices thereof.

15. In an arc quenching structure a plurality of spaced notched plates,the said notches being substantially aligned to form an arcing path,each of said plates having a pair of legs defining each notch;corresponding legs on corresp nding sides of the plates being alignedwith each other; opposed side wall for said are quencher: said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; extensions from the outer edges of said plates extendingthrough said side walls and securing said plates and side wallstogether, said extensions from opposite edges of the plates beingstaggered with respect to each other: said plates being arranged so thatadjacent plates are reversed with respect to each other wherebyextensions through each side wall are staggered, said extensions havingshoulders at their bases for spacing the outer edges of the plates fromsaid side walls, a top plate secured to the ends of said notched platesand enga in said side walls; said top plate, notched plates and sidewalls interbracing and supporting each other.

18. In a circuit interrupter having a stationary contact and acomplementary contact movable between positions of disengagement and entwith said stationary contact, an are 4 quenching structure comprisingspaced notched a metal plates, one end plate of said structureelectrically-and mechanically connected to said stationai'ycontact. ametallic arcing horn secured to the other end plate in closely spacedrelation with said movable contact when in said disengaged position,said arcing horn being electrically connected to said movable contact,the notches in said plates being substantially aligned, each .of saidplates havinga pair of legs deilningeach notch; corresponding legs oncorresponding sides.

of the 'plat'es'being aligned with each other; op-

posed side walls for said are quencher; said plates being each normal toand supported by said side walls at the outer edges of said plates;extensions from the outer edgu of said plates extending through saidside-walls and securing said plates terminal structure and extendingfrom a surface thereof, an extension of said stationary contact inspaced relation to said surface of said ter- 'minal structure, an arcquenching structure comprising spaced notched metal plates, an end plateof said quenching structure in contact with said terminal structure andpositioned by the cooperation of its notch with said stationary contactand the extension thereof, a plurality of said plates having notchessubstantially aligned,

each of said plates having a pair of legs defining each notch;corresponding legs on corresponding sides of the plates being alignedwith each other; opposed side walls for said are quencher; said platesbeing each normal to and supported by said side walls at the outer edgesof said plates; extensions from the outer edges of said plates extendingthrough said side walls and securing said plates and side wallstogether, said extensions from opposite edges of the plates beingstaggered with respect to each other; said plates being arranged so thatadjacent plates are reversed with respect to each other wherebyextensions through each side wall are staggered, a top plate secured'tothe ends of said notched plates and engaging said side walls; said topplate, notched plates and side walls interbracing and supporting eachother. c

"18. In'a circuit interrupter having a stationary contact and acomplementary contact movable between positions of disengagement andengagement with said stationa'ry contact, an arc quenching structurecomprising spaced notched metal plates, one end plate of said structureelectrically and mechanically connected to said stationarycontact, ametallic arcing horn secured to the other end plate in closely spacedrelation with said movable contact when in said disengaged position.said arcing horn being electrically connected to said movable contact,the notches in said plates being substantially aligned, each of saidplates having a pair of legs defining each notch: corresponding legs oncorresponding sides of the plates being aligned with each other; opposedside walls for said arc quencher; said plates being each normal to andsupported by said side walls at the outer edges of said plates; is topplate secured to the ends of said notched plates and engaging said sidewalls; said top in spaced relation to said surface of said terand sidewalls together, said extensions from opposite edgesof the plates beingstaggered with respect to each other: said plates being arranged so thatadjacent plates are reversed with respect to each other wherebyextensions through each side wall are staggered,- a top plate secured tothe ends, of said notched plates and said sick walls: said top plate,notched plates and zigserwalls interbracing and, supporting each""l'!*.*In-a;circuit interrupter having terminal structure, a stationarycontact moimted on said plate, notched plates and side wallsinterbracing and supporting each other.

19. In a circuit interrupter having terminal structure, a stationarycontact moimted on said terminalstructure and extending from a surfacethereof, an extensionof said stationary contact minal structure, an arcquenching structure comprising spaced notched metal plates, an end plateof said quenching structure in contact with said terminal structure andpositioned by the cooperation of its notch with said stationary contactand the extension thereof, a plurality of said plates having notchessubstantially aligned, each of said plates having a pair of legsdefining each notch; corresponding legs on corresponding sides of theplates being aligned with each other; opposed side walls for said arequencher: said plates being each normal to and supported by said sidewalls at the outer edges of said plates: a top plate secured to the endsof said notched plates and engaging said side walls: said top plate,notched plates, and side walls interbracing and supporting each other.

= C. GRAVES, Ja.

